Better wording for code comment

Co-authored-by: Cas Donoghue <[email protected]>

Author: andsel

logstash-core/lib/logstash/api/commands/stats.rb

@@ -176,7 +176,8 @@ def refine_batch_metrics(stats)
             # current is a tuple of [event_count, byte_size] store the reference locally to avoid repeatedly
             # reading and retrieve unrelated values
             current_data_point = stats[:batch][:current]
-            # average return a FlowMetric which and we need to invoke getValue to obtain the map with metric details.
+# FlowMetric (from stats[:batch][:event_count][:average]) returns a composite object containing lifetime/last_1_minute/etc values. In order to get the map of sub-metrics we must use `.value`.
+# See: https://github.com/elastic/logstash/blob/279171b79c1f3be5fc85e6e2e4092281e504a6f9/logstash-core/src/main/java/org/logstash/instrument/metrics/ExtendedFlowMetric.java#L89
             event_count_average_flow_metric = stats[:batch][:event_count][:average].value
             event_count_average_lifetime = event_count_average_flow_metric["lifetime"] ? event_count_average_flow_metric["lifetime"].round : 0
             byte_size_average_flow_metric = stats[:batch][:byte_size][:average].value